13C-NMR study of glucose and pyruvate catabolism in four acetogenic species isolated from the human colon

Abstract

Glucose fermentation by four acetogenic species (two Clostridium strains, one Streptococcus strain and Ruminococcus hydrogenotrophicus) isolated from the human colon was of a mixed-acid type, whereas pyruvate metabolism was characterised by homoacetogenesis. Acetate formation from [1-13C] and [2-13C]glucose was consistent with the formation of acetyl-SCoA from pyruvate generated by the Embden-Meyerhof-Parnas pathway. Labelling of lactate and ethanol demonstrated that these metabolites were formed by reduction of pyruvate and acetyl-SCoA, respectively. In contrast, the reductive pathway of acetate formation was the preferential means of re-oxidising cofactors formed during [1-13C]pyruvate catabolism.